Abstract

We demonstrate that conically tapered cylindrical apertures can be used to efficiently concentrate broadband terahertz (THz) radiation. Keeping the aperture diameter on the input plane fixed, we show that as the diameter of the aperture on the exit plane is decreased, we obtain an increase in the magnitude of the transmitted electric field that varies inversely with the output aperture diameter. Correspondingly, the transmitted THz intensity concentration increases inversely with the square of the output aperture diameter. For the smallest aperture that we fabricated, we obtain a ~50 fold increase in the transmitted THz intensity. We expect further increases in the intensity concentration with smaller output apertures. As the output aperture diameter is decreased with a corresponding increase in the concentration factor, we directly measure an increase in the propagation time delay of a narrowband pulse through the structure. Finally, we demonstrate that further increase in the concentration factor can be achieved by engraving circular grooves around the input aperture.

© 2010 OSA

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References

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    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
  3. A. J. Babadjanyan, N. L. Margaryan, and K. V. Nerkararyan, “Superfocusing of surface polaritons in the conical structure,” J. Appl. Phys. 87(8), 3785–3788 (2000).
    [CrossRef]
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    [CrossRef] [PubMed]
  5. N. A. Janunts, K. S. Baghdasaryan, K. V. Nerkararyan, and B. Hecht, “Excitation and superfocusing of surface plasmon polaritons on a silver-coated optical fiber tip,” Opt. Commun. 253(1-3), 118–124 (2005).
    [CrossRef]
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    [CrossRef]
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    [CrossRef]
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2010 (2)

J. A. Schuller, E. S. Barnard, W. Cai, Y. C. Jun, J. S. White, and M. L. Brongersma, “Plasmonics for extreme light concentration and manipulation,” Nat. Mater. 9(3), 193–204 (2010).
[CrossRef] [PubMed]

H. Zhan, R. Mendis, and D. M. Mittleman, “Superfocusing terahertz waves below λ/250 using plasmonic parallel-plate waveguides,” Opt. Express 18(9), 9643–9650 (2010).
[CrossRef] [PubMed]

2009 (1)

2008 (3)

2007 (1)

K. C. Vernon, D. K. Gramotnev, and D. F. P. Pile, “Adiabatic nanofocusing of plasmons by a sharp metal wedge on a dielectric substrate,” J. Appl. Phys. 101(10), 104312 (2007).
[CrossRef]

2006 (4)

T. Matsui, Z. V. Vardeny, A. Agrawal, A. Nahata, and R. Menon, “Resonantly-enhanced transmission through a periodic array of subwavelength apertures in heavily-doped conducting polymer films,” Appl. Phys. Lett. 88(7), 071101 (2006).
[CrossRef]

E. Ozbay, “Plasmonics: merging photonics and electronics at nanoscale dimensions,” Science 311(5758), 189–193 (2006).
[CrossRef] [PubMed]

A. V. Zayats and I. I. Smolyaninov, “High-optical-throughput individual nanoscale aperture in a multilayered metallic film,” Opt. Lett. 31(3), 398–400 (2006).
[CrossRef] [PubMed]

P. Ginzburg, D. Arbel, and M. Orenstein, “Gap plasmon polariton structure for very efficient microscale-to-nanoscale interfacing,” Opt. Lett. 31(22), 3288–3290 (2006).
[CrossRef] [PubMed]

2005 (3)

A. Agrawal, H. Cao, and A. Nahata, “Excitation and scattering of surface plasmon-polaritons on structured metal films and their application to pulse shaping and enhanced transmission,” N. J. Phys. 7, 249 (2005).
[CrossRef]

N. A. Janunts, K. S. Baghdasaryan, K. V. Nerkararyan, and B. Hecht, “Excitation and superfocusing of surface plasmon polaritons on a silver-coated optical fiber tip,” Opt. Commun. 253(1-3), 118–124 (2005).
[CrossRef]

A. Agrawal, H. Cao, and A. Nahata, “Time-domain analysis of enhanced transmission through a single subwavelength aperture,” Opt. Express 13(9), 3535–3542 (2005).
[CrossRef] [PubMed]

2004 (2)

M. I. Stockman, “Nanofocusing of optical energy in tapered plasmonic waveguides,” Phys. Rev. Lett. 93(13), 137404 (2004).
[CrossRef] [PubMed]

J. B. Pendry, L. Martín-Moreno, and F. J. Garcia-Vidal, “Mimicking surface plasmons with structured surfaces,” Science 305(5685), 847–848 (2004).
[CrossRef] [PubMed]

2001 (1)

2000 (1)

A. J. Babadjanyan, N. L. Margaryan, and K. V. Nerkararyan, “Superfocusing of surface polaritons in the conical structure,” J. Appl. Phys. 87(8), 3785–3788 (2000).
[CrossRef]

1998 (1)

L. Novotny, E. J. Sanchez, and X. S. Xie, “Near-field optical imaging using metal tips illuminated by higher order Hermite-Gaussian beams,” Ultramicroscopy 71(1-4), 21–29 (1998).
[CrossRef]

1983 (1)

Agrawal, A.

A. Agrawal, Z. V. Vardeny, and A. Nahata, “Engineering the dielectric function of plasmonic lattices,” Opt. Express 16(13), 9601–9613 (2008).
[CrossRef] [PubMed]

T. Matsui, Z. V. Vardeny, A. Agrawal, A. Nahata, and R. Menon, “Resonantly-enhanced transmission through a periodic array of subwavelength apertures in heavily-doped conducting polymer films,” Appl. Phys. Lett. 88(7), 071101 (2006).
[CrossRef]

A. Agrawal, H. Cao, and A. Nahata, “Excitation and scattering of surface plasmon-polaritons on structured metal films and their application to pulse shaping and enhanced transmission,” N. J. Phys. 7, 249 (2005).
[CrossRef]

A. Agrawal, H. Cao, and A. Nahata, “Time-domain analysis of enhanced transmission through a single subwavelength aperture,” Opt. Express 13(9), 3535–3542 (2005).
[CrossRef] [PubMed]

Alexander, R. W.

Arbel, D.

Babadjanyan, A. J.

A. J. Babadjanyan, N. L. Margaryan, and K. V. Nerkararyan, “Superfocusing of surface polaritons in the conical structure,” J. Appl. Phys. 87(8), 3785–3788 (2000).
[CrossRef]

Baghdasaryan, K. S.

N. A. Janunts, K. S. Baghdasaryan, K. V. Nerkararyan, and B. Hecht, “Excitation and superfocusing of surface plasmon polaritons on a silver-coated optical fiber tip,” Opt. Commun. 253(1-3), 118–124 (2005).
[CrossRef]

Barnard, E. S.

J. A. Schuller, E. S. Barnard, W. Cai, Y. C. Jun, J. S. White, and M. L. Brongersma, “Plasmonics for extreme light concentration and manipulation,” Nat. Mater. 9(3), 193–204 (2010).
[CrossRef] [PubMed]

Bartal, G.

Bell, R. J.

Bell, R. R.

Bell, S. E.

Brongersma, M. L.

J. A. Schuller, E. S. Barnard, W. Cai, Y. C. Jun, J. S. White, and M. L. Brongersma, “Plasmonics for extreme light concentration and manipulation,” Nat. Mater. 9(3), 193–204 (2010).
[CrossRef] [PubMed]

Cai, W.

J. A. Schuller, E. S. Barnard, W. Cai, Y. C. Jun, J. S. White, and M. L. Brongersma, “Plasmonics for extreme light concentration and manipulation,” Nat. Mater. 9(3), 193–204 (2010).
[CrossRef] [PubMed]

Cao, H.

A. Agrawal, H. Cao, and A. Nahata, “Excitation and scattering of surface plasmon-polaritons on structured metal films and their application to pulse shaping and enhanced transmission,” N. J. Phys. 7, 249 (2005).
[CrossRef]

A. Agrawal, H. Cao, and A. Nahata, “Time-domain analysis of enhanced transmission through a single subwavelength aperture,” Opt. Express 13(9), 3535–3542 (2005).
[CrossRef] [PubMed]

Choi, H.

Durach, M.

Ebbesen, T. W.

Garcia-Vidal, F. J.

J. B. Pendry, L. Martín-Moreno, and F. J. Garcia-Vidal, “Mimicking surface plasmons with structured surfaces,” Science 305(5685), 847–848 (2004).
[CrossRef] [PubMed]

Ginzburg, P.

Gramotnev, D. K.

K. C. Vernon, D. K. Gramotnev, and D. F. P. Pile, “Adiabatic nanofocusing of plasmons by a sharp metal wedge on a dielectric substrate,” J. Appl. Phys. 101(10), 104312 (2007).
[CrossRef]

Hecht, B.

N. A. Janunts, K. S. Baghdasaryan, K. V. Nerkararyan, and B. Hecht, “Excitation and superfocusing of surface plasmon polaritons on a silver-coated optical fiber tip,” Opt. Commun. 253(1-3), 118–124 (2005).
[CrossRef]

Janunts, N. A.

N. A. Janunts, K. S. Baghdasaryan, K. V. Nerkararyan, and B. Hecht, “Excitation and superfocusing of surface plasmon polaritons on a silver-coated optical fiber tip,” Opt. Commun. 253(1-3), 118–124 (2005).
[CrossRef]

Jun, Y. C.

J. A. Schuller, E. S. Barnard, W. Cai, Y. C. Jun, J. S. White, and M. L. Brongersma, “Plasmonics for extreme light concentration and manipulation,” Nat. Mater. 9(3), 193–204 (2010).
[CrossRef] [PubMed]

Kuipers, L. K.

Lezec, H. J.

Linke, R. A.

Long, L. L.

Margaryan, N. L.

A. J. Babadjanyan, N. L. Margaryan, and K. V. Nerkararyan, “Superfocusing of surface polaritons in the conical structure,” J. Appl. Phys. 87(8), 3785–3788 (2000).
[CrossRef]

Martín-Moreno, L.

J. B. Pendry, L. Martín-Moreno, and F. J. Garcia-Vidal, “Mimicking surface plasmons with structured surfaces,” Science 305(5685), 847–848 (2004).
[CrossRef] [PubMed]

Matsui, T.

T. Matsui, Z. V. Vardeny, A. Agrawal, A. Nahata, and R. Menon, “Resonantly-enhanced transmission through a periodic array of subwavelength apertures in heavily-doped conducting polymer films,” Appl. Phys. Lett. 88(7), 071101 (2006).
[CrossRef]

Mendis, R.

Menon, R.

T. Matsui, Z. V. Vardeny, A. Agrawal, A. Nahata, and R. Menon, “Resonantly-enhanced transmission through a periodic array of subwavelength apertures in heavily-doped conducting polymer films,” Appl. Phys. Lett. 88(7), 071101 (2006).
[CrossRef]

Mittleman, D. M.

Nahata, A.

A. Agrawal, Z. V. Vardeny, and A. Nahata, “Engineering the dielectric function of plasmonic lattices,” Opt. Express 16(13), 9601–9613 (2008).
[CrossRef] [PubMed]

T. Matsui, Z. V. Vardeny, A. Agrawal, A. Nahata, and R. Menon, “Resonantly-enhanced transmission through a periodic array of subwavelength apertures in heavily-doped conducting polymer films,” Appl. Phys. Lett. 88(7), 071101 (2006).
[CrossRef]

A. Agrawal, H. Cao, and A. Nahata, “Excitation and scattering of surface plasmon-polaritons on structured metal films and their application to pulse shaping and enhanced transmission,” N. J. Phys. 7, 249 (2005).
[CrossRef]

A. Agrawal, H. Cao, and A. Nahata, “Time-domain analysis of enhanced transmission through a single subwavelength aperture,” Opt. Express 13(9), 3535–3542 (2005).
[CrossRef] [PubMed]

Nam, S.

Nelson, K. A.

Nerkararyan, K. V.

N. A. Janunts, K. S. Baghdasaryan, K. V. Nerkararyan, and B. Hecht, “Excitation and superfocusing of surface plasmon polaritons on a silver-coated optical fiber tip,” Opt. Commun. 253(1-3), 118–124 (2005).
[CrossRef]

A. J. Babadjanyan, N. L. Margaryan, and K. V. Nerkararyan, “Superfocusing of surface polaritons in the conical structure,” J. Appl. Phys. 87(8), 3785–3788 (2000).
[CrossRef]

Novotny, L.

L. Novotny, E. J. Sanchez, and X. S. Xie, “Near-field optical imaging using metal tips illuminated by higher order Hermite-Gaussian beams,” Ultramicroscopy 71(1-4), 21–29 (1998).
[CrossRef]

Ordal, M. A.

Orenstein, M.

Ozbay, E.

E. Ozbay, “Plasmonics: merging photonics and electronics at nanoscale dimensions,” Science 311(5758), 189–193 (2006).
[CrossRef] [PubMed]

Pellerin, K. M.

Pendry, J. B.

J. B. Pendry, L. Martín-Moreno, and F. J. Garcia-Vidal, “Mimicking surface plasmons with structured surfaces,” Science 305(5685), 847–848 (2004).
[CrossRef] [PubMed]

Pile, D. F.

Pile, D. F. P.

K. C. Vernon, D. K. Gramotnev, and D. F. P. Pile, “Adiabatic nanofocusing of plasmons by a sharp metal wedge on a dielectric substrate,” J. Appl. Phys. 101(10), 104312 (2007).
[CrossRef]

Polman, A.

Rusina, A.

Sanchez, E. J.

L. Novotny, E. J. Sanchez, and X. S. Xie, “Near-field optical imaging using metal tips illuminated by higher order Hermite-Gaussian beams,” Ultramicroscopy 71(1-4), 21–29 (1998).
[CrossRef]

Schuller, J. A.

J. A. Schuller, E. S. Barnard, W. Cai, Y. C. Jun, J. S. White, and M. L. Brongersma, “Plasmonics for extreme light concentration and manipulation,” Nat. Mater. 9(3), 193–204 (2010).
[CrossRef] [PubMed]

Smolyaninov, I. I.

Stockman, M. I.

Thio, T.

Vardeny, Z. V.

A. Agrawal, Z. V. Vardeny, and A. Nahata, “Engineering the dielectric function of plasmonic lattices,” Opt. Express 16(13), 9601–9613 (2008).
[CrossRef] [PubMed]

T. Matsui, Z. V. Vardeny, A. Agrawal, A. Nahata, and R. Menon, “Resonantly-enhanced transmission through a periodic array of subwavelength apertures in heavily-doped conducting polymer films,” Appl. Phys. Lett. 88(7), 071101 (2006).
[CrossRef]

Verhagen, E.

Vernon, K. C.

K. C. Vernon, D. K. Gramotnev, and D. F. P. Pile, “Adiabatic nanofocusing of plasmons by a sharp metal wedge on a dielectric substrate,” J. Appl. Phys. 101(10), 104312 (2007).
[CrossRef]

Ward, C. A.

White, J. S.

J. A. Schuller, E. S. Barnard, W. Cai, Y. C. Jun, J. S. White, and M. L. Brongersma, “Plasmonics for extreme light concentration and manipulation,” Nat. Mater. 9(3), 193–204 (2010).
[CrossRef] [PubMed]

Xie, X. S.

L. Novotny, E. J. Sanchez, and X. S. Xie, “Near-field optical imaging using metal tips illuminated by higher order Hermite-Gaussian beams,” Ultramicroscopy 71(1-4), 21–29 (1998).
[CrossRef]

Zayats, A. V.

Zhan, H.

Zhang, X.

Appl. Opt. (1)

Appl. Phys. Lett. (1)

T. Matsui, Z. V. Vardeny, A. Agrawal, A. Nahata, and R. Menon, “Resonantly-enhanced transmission through a periodic array of subwavelength apertures in heavily-doped conducting polymer films,” Appl. Phys. Lett. 88(7), 071101 (2006).
[CrossRef]

J. Appl. Phys. (2)

K. C. Vernon, D. K. Gramotnev, and D. F. P. Pile, “Adiabatic nanofocusing of plasmons by a sharp metal wedge on a dielectric substrate,” J. Appl. Phys. 101(10), 104312 (2007).
[CrossRef]

A. J. Babadjanyan, N. L. Margaryan, and K. V. Nerkararyan, “Superfocusing of surface polaritons in the conical structure,” J. Appl. Phys. 87(8), 3785–3788 (2000).
[CrossRef]

N. J. Phys. (1)

A. Agrawal, H. Cao, and A. Nahata, “Excitation and scattering of surface plasmon-polaritons on structured metal films and their application to pulse shaping and enhanced transmission,” N. J. Phys. 7, 249 (2005).
[CrossRef]

Nat. Mater. (1)

J. A. Schuller, E. S. Barnard, W. Cai, Y. C. Jun, J. S. White, and M. L. Brongersma, “Plasmonics for extreme light concentration and manipulation,” Nat. Mater. 9(3), 193–204 (2010).
[CrossRef] [PubMed]

Opt. Commun. (1)

N. A. Janunts, K. S. Baghdasaryan, K. V. Nerkararyan, and B. Hecht, “Excitation and superfocusing of surface plasmon polaritons on a silver-coated optical fiber tip,” Opt. Commun. 253(1-3), 118–124 (2005).
[CrossRef]

Opt. Express (6)

Opt. Lett. (3)

Phys. Rev. Lett. (1)

M. I. Stockman, “Nanofocusing of optical energy in tapered plasmonic waveguides,” Phys. Rev. Lett. 93(13), 137404 (2004).
[CrossRef] [PubMed]

Science (2)

E. Ozbay, “Plasmonics: merging photonics and electronics at nanoscale dimensions,” Science 311(5758), 189–193 (2006).
[CrossRef] [PubMed]

J. B. Pendry, L. Martín-Moreno, and F. J. Garcia-Vidal, “Mimicking surface plasmons with structured surfaces,” Science 305(5685), 847–848 (2004).
[CrossRef] [PubMed]

Ultramicroscopy (1)

L. Novotny, E. J. Sanchez, and X. S. Xie, “Near-field optical imaging using metal tips illuminated by higher order Hermite-Gaussian beams,” Ultramicroscopy 71(1-4), 21–29 (1998).
[CrossRef]

Other (1)

N. Marcuvitz, Waveguide Handbook, (New York: McGraw-Hill, 1951).

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Figures (5)

Fig. 1
Fig. 1

Schematic diagram of the experimental setup and details of the TA structure. (a) A schematic diagram of the THz time-domain spectroscopy apparatus. A collimated THz beam is normally incident on a conically tapered circular aperture. The radiated electromagnetic wave is detected using a transient photoconductive device. For all TA structures the input diameter, D1, is fixed at 1.9 mm and the taper angle, α, is fixed at 15°. The smaller output diameter, D2, varies between 200 and 800 µm and determines the length, L of the TA structure. (b) A picture of a typical TA cross-section; the TA structure is fabricated in a titanium lead blend.

Fig. 2
Fig. 2

Spectral transmission properties of a TA structure with D1 = 1.9 mm and D2 = 440 µm. (a) Amplitude spectrum for (i) 1.9 mm diameter single aperture in a 25 µm thick film (reference); (ii) 440 μm diameter single aperture in a 25 µm thick film; and (iii) 5.55 mm thick TA with D2 = 440μm. (b) Transmission efficiency of the TA aperture (red) and the 440 µm reference aperture (green) in the frequency domain. Inset, spectrum of the transmission amplitude concentration factor, fE(ν). (c) Electric field concentration for various TA structures as a function of the output aperture diameter, D2. The solid line through the data points is a fit to a 1/D2 dependence. Inset to (c) The obtained value for the transmission turn-on frequency for the TA structures versus D2. These values correspond to the cutoff frequency, νc of the circular apertures, as demonstrated by the fit to the equation for the cutoff frequency, νc = 1.841c/(πD2).

Fig. 3
Fig. 3

Numerical simulation of the field properties related to the TA structure. (a) A snapshot of the electric field inside and around a conical TA structure having D2 = 440 µm. A broadband vertically polarized THz electric field is incident on the TA from the right. The metal (grey region) is modeled as a perfect electrical conductor with D1 = 1.9 mm and D2 = 440 µm. (b) The enhancement spectrum f E ( ν ) = t x , T A E ( ν ) / t x E ( ν ) for various D2 values. (c) Field concentration spectra, fE(ν) of TA structures for various D2. The experimental results from Fig. 2(c) are shown for comparison and the solid line is a fit to a 1/D2 dependence. Inset to (c) The value of the transmission turn-on frequency of the TA structure versus D2 obtained from the numerical simulations. These values correspond to the cutoff frequency of the circular apertures, νc = 1.841c/(πD2).

Fig. 4
Fig. 4

Group velocity delay measurements. (a) Group velocity delay as a function of frequency obtained from the measured relative phase difference (inset). (b) Time domain transmission measurements using a narrowband THz pulse centered at ~0.4 THz with a line width of ~40 GHz. The time delay τ = 3.6 ps is in good agreement with τ = 3.5 ps at 0.4 THz obtained from Fig. 4(a). (c) The amplitude of the narrow band THz pulse in frequency domain. (d) The group velocity delay obtained via experiment and simulation. The black line is a linear fit to the experimental data based on a THz group velocity of 0.8c. The green line shows the expected group delay if the wave simply propagated along the conically tapered wall of the aperture with a group velocity of c.

Fig. 5
Fig. 5

Enhancement of the transmission spectrum through a TA with annular grooves surrounding the input aperture relative to an identical bare TA structure. The enhancement at ν~0.3 THz corresponds to the resonance condition with center-to-center ring spacing of 1 mm. (Inset) An optical micrograph of the TA cross-section with D1 = 1.9 mm and D2 = 470 µm. The grooves are 500 µm wide and ~100 µm deep, with a center-to-center spacing of 1 mm. The structure is fabricated in a titanium lead blend.

Equations (1)

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τ = 1 2 π φ ( ν ) ν ..

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